Plastic deformation imaging film and process



' March 7, 1967 SIZE OF OH BAND INFRARED w. G'UNDLACH PLASTIC DEFORMATION IMAGING FILM AND PROCESS Filed June 5, 1963 APPLY CHARGE PATTERN SOFTEN HARDEN.

PERMANENTLY HARDEN BY UNIFORM EXPOSURE o U.V. EXPOSURE- HOURS 'SELECTIV'ELY HARDEN BY EXPOSURE YAPPLY UNIFORM CHARGE SOFTEN HARDEN PER MANENTLY HARD EN BY UNIFORM EXPOSURE INVENTOR. ROBERT W. GUNDLACH ATTORNEY United States Patent 3,307,941 PLASTIC DEFORMATION IMAGING FILM AND PROCESS Robert W. Gundlach, Victor, N.Y., assignor to Xerox Corporation, Rochester, N .Y., a corporation of New York Filed June 3, 1963, Ser. No. 284,962 5 Claims. (Cl. 961.1)

This invention relates generally to xerography and more specifically to novel electrostatic techniques for the formation of visible images.

In the most commonly practiced forms of xerography, an electrostatic latent image is formed by the combined action of an electric field and a pattern of electromagnetic radiation, such as visible light, on a photoconductive insulating layer. The latent electrostatic image is then generally converted to a visible image by utilizing the electrostatic image to control the deposition of finely-divided colored electroscopic developing material on the surface bearing the latent electrostatic image. After the visible image is formed, it is usually fixed in place on the surface of the photoconductive insulator or transferred to a second surface and fixed thereon depending upon whether or not the photoconductive insulator is reusable. Reference is made to US. Patent 2,297,691 to Carlson for a more detailed description of the basic process.

A variety of Xerographic methods are known which generally conform to the above description and which enjoy widespread commercial use. A new technique for making latent electrostatic images visible known as frost development has recently been devised and is more fully described in an article entitled, A Cyclic Xerographic Method Based on Frost Deformation, by R. W. Gundlach and C. J. Claus appearing in the January-February 1963 issue of the Journal of Photographic Science and Engineering. Basically, this new technique involves apply ing a latent electrostatic image or charge pattern to-an insulating film which is softenable as by the application of heat or a solvent vapor and softening the film until the electrostatic repulsion forces of the charge pattern eX- ceed the surface tension forces of the film. When this critical or threshold condition is met, a series of very small surface folds or wrinkles are formed on the film with the depth of these folds in any particular surface area of the film being dependent upon the amount of charge in that area, thus giving the image a frosted appearance. Actually, the film may be softened prior to the application of the charge pattern so long-as it is sufliciently insulating to hold the charge, the basic requireinent being that the charge pattern be on the film while it issoft. This generally requires highly insulating films; however, in cases where charging may be contiued during softening films with relatively low resistivities on the order of about 10 ohm-cm. may be employed. These lower resistivity films are also referred to as insulating for purposes of this description. This frost image is then frozen by allowing or causing the film to reharden as by removing the heat or solvent vapors or in the case of a material which at room temperature is sufficiently soft to frost under the influence of a deposited charge pattern by cooling the material. It has also been found possible to erase such images after use by simply resoftening the film and maintaining a low viscosity for a sufiicient period of time. Discharge is believed to occur during this re softening by fluid migration of the ions making up the charge pattern on the top surface of the frosted film whereupon surface tension forces restore a smooth surface to the film.

Now in accordance with the present invention, it has been found that materials made up of mixtures of photopolymers and frostable resins may be caused to harden by exposure to radiation such as ultraviolet light and that this hardening by exposure may be used to permanently fix frost images, making them nonerasable by significantly raising their resistance to softening agents such as heat or solvents. It has also been found that such frostable materials may be selectively hardened prior to the frosting process and that such hardening may be caused to occur in a pattern of an image which is to be reproduced. For example, the frostable material may be uniformly charged and uniformly subjected to heat, solvent vapor or other softening action in which case frosting occurs only in those areas of the material which have not been previously hardened byexposure. With this latter technique, charge pattern modulating devices such as photoconductive insulators which are used in the ordinary frost process to apply charge to the frostable layer in a pattern which conforms with the image to be reproduced are eliminated from the system, because the charge pattern to be laid down on the frostable resin is uniform. i

In addition, the film may be uniformly prefrosted and exposed to an image with hardening radiation whereupon a subsequent softening step erases the frost pattern only in nonimage areas. Although the materials of this in vention are generally described in terms of the frost process they may also be employed in toher types of electrostatic charge-induced plastic deformation processes. For example, relief imaging is a similar system in which defor mati-on occurs only in lines at areas on the film of high potential gradient, after charging and softening.

Other objects, features, and advantages of'the present invention will become apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein;

FIG. 1 is a process flow diagram of a modified form of the Xerographic frost process which may employ the materials of this invention;

FIG. 2 is a process flow diagram of a modified form of the Xerographic frost process which may employ the materials of this invention;

FIG. 3 is a graph showing the duration of ultraviolet exposure of a frostable film versus the size of its hydroxyl band on infrared analysis; FIG.. 4 is an apparatus using the FIG. 2 process. Referring now to FIG. 1 of the drawings where exemplary process steps for the use of the materials of this invention are illustrated, it is seen that a charge pattern is first applied to the frostable layer. This charge pat tern conforms with the image to be reproduced, and may be applied by any of the techniques described in the Gundlach-Claus publication referred to' above or in a copending application S.N. 193,277 filed May 8, 1962, now US. Patent No. 3,196,011, and entitled, Electrostatic Frosting. Frequently, although not always, the charge deposition technique involvesplacing the insulating frostable material in close proximity to a photoconductor with a grounded conductive substrate and exposing the photoconductor to the light image to be reproduced. This exposure, by modulating the conductivity of the photoconductor, controls the amount of charge which is reflected through the frostable film. In other techniques, charge patterns are formed on photoconductive insulators as they are in the ordinary method of Xerographic reproduction and then transferred to the insulating frostable layer by bringing the two into very insulating frostable layer by the Tesi discharge technique as more fully described in U.S. Patents 3,023,731 and 2,919,967 both to Schwertz or by the techniques described in US. Patents 3,001,848 and 3,001,849 both to Walkup. The second step in the process is to soften the frostable layer bearing its electrostatic charge pattern to a viscosity at which the repulsive forces of the charge pattern on the frostable layer overcome the surface tension forces of the layer so that the wrinkled frost pattern of ridges and valleys conforming to the charge pattern forms on the surface of the front layer. This step need not necessarily be carried out subsequent to the application of the charge pattern, but instead the charge pattern may be applied to a simultaneously softened or pre-softened film so that frosting occurs on the film sur face simultaneously with charge deposition. As described more fully in the above referenced patent application and publication, this softening may be accomplished by different techniques which may, for example, include the application of heat if the frostable layer is thermally softenable or by the use of vapors containing a solvent for the frostable film. It should be noted that the film need not be softened through its whole thickness but that it is only necessary to soften the upper portion of the film where the deformation occurs. Of course, as film thickness decreases, this makes up an ever increasing percentage of the film thickness.

The next step in the process is to reharden the frosted layer which may, for example, be accomplished by removal of the solvent vapor or heat so that the frost image is frozen. It should be noted at this point that a frostable material which is initially soft may be utilized thus eliminating the softening step described above. Thus, material which is relatively soft or viscous at room temperatures, may be frosted by merely applying the charge pattern as desired. It is, however, important that the charge pattern be frozen within a relatively short time after the formation of the frost image whether the image is formed on a material which is initially soft or one which is softened during or subsequent to charge deposition, because excessive or overlong softening of the frostable layer permits the charge which forms the charge pattern to flow through the frostable layer so that surface tension forces tend to restore the smooth surface of the layer thereby destroying the image. In fact, this technique may be used for erasing the image after it is utilized and the erased film may be used to reform a new image during a later recycling of the process.

Although erasable films are valuable in some applications, they are undesirable for other applications because they cannot be used with assurance as truly permanent images. In many instances, it is, therefore, highly desirable to permanently harden the frost images after they have been formed as is indicated by the fourth step of the FIG. 1 process. This permanent hardening is preferably accomplished by exposing the frosted layer to a source of electromagnetic radiation which may, for example, be light, since such a hardening technique is both simple and inexpensive. Furthermore, hardening by exposure makes the process described below in connection with FIG. 2 feasible.

In this second process, the frostable film is first selectively hardened by exposing the film to a radiation image of the original to be reproduced. Thus, for example, the film is exposed to an ultraviolet image of the original until it is hardened in areas corresponding to nonimage areas of the original. If the process is begun with this selective permanent hardening by exposure, it is unnecessary to apply the charge in a pattern since frosting will take place only in unhardened areas when the films is softened. Instead, the charge is applied uniformly over the surface of the selectively exposure-hardened film. This charging may be accomplished by any one of a number of known techniques including any one of those commonly used in the xerographic reproduction process.

More specifically, this charging may be accomplished with a corona generating unit as described in US. Patents 2,588,699 to Carlson and 2,778,946 to Mayo. The frostable film is then softened, as for example, by the heat or solvent techniques described in connection with the FIG. 1 process, until the frost pattern appears on the film. As shall be described more fully hereinafter, the degree of selective hardening by initial exposure may vary depending upon the amount and intensity of exposure, the addition of radiation sensitizers to the frostable film and the like. It should be apparent, therefore, that if the initial selective hardening by exposure has not been sufficient to impart a significant degree of difference between the softening points of exposed and unexposed portions of the film, care should be taken in application of the softening means so that the film is not softened in all areas thereby allowing the formation of a uniform frost pattern over the whole surface of the film. In the case of larger differentials in the degree of initial hardening by selective exposure, it is not necessary to exercise so much care in carrying out the softening step. This softening step is then followed by freezing or temporary hardening of the frost image by removal of the softening agents as in the FIG. 1 process and optionally by permanent hardening of the whole film with its frost image by uniform exposure of the whole film with radiation similar to that of the first step of the process.

In an alternative mode of operation of the FIG. 2 process the film may first be uniformly frosted by charging, softening, and freezing. It may then be permanently hardened in image configuration by exposure to an image to be reproduced with an actinic energy source so that when a softening agent such as heat or solvent vapor is applied to the film for a sufiicient period, the unexposed areas are erased, leaving the preformed frost wrinkles on the film in the image areas. The advantage of this technique is that the film may be obtained in the prefrosted condition from the manufacturer and the only equipment needed by the customer for forming images is an energy source and a fihn softening apparatus.

If desired, the last two steps of either the process of FIG. 1 or the process of FIG. 2 may be combined so that hardening is accomplished solely by uniform exposure. In this way, the film need not necessarily be separated from the softening agents in order to achieve hardening. In that instance, for example, the whole process could be carried out while the frostable film was moving through a solvent vapor atmosphere or through a heated chamber.

In FIG. 4 there is illustrated an exemplary frost imaging apparatus which operates according to the FIG. 2 process. In this embodiment a frostable film 11 of one of the materials described hereinafter is fed into the system from a supply roll 12. The film is then exposed to an ultraviolet light projection of the image to be reproduced by projector 13 thus selectively hardening the film in areas which correspond to the transparent sections of the projected image. The film then passes under a charging unit 14 of the corona discharge type described above where a uniform layer of charge is deposited over the whole of the film. As shown in this view, the film is backed by a conductive stationary grounded plate 16 so that charge will deposit upon the film. In the alternative, however, the film may be initially formed on a thin conductive foil such as aluminum or brass. The film then passes over two idle rollers 17 While passing beneath a softening unit which in this instance is an electrical resistance heating unit shown in side section. This heating unit is set so as to generate sufficient heat to soften unexposed areas and consequently unhardened areas of the film 11 to the point where a frost pattern appears on those areas while not generating sufiicient, heat to soften or burn exposed and hardened film areas. As explained above, a solvent vapor atmosphere may be provided for the film at this point in the processing cycle in place of the resistance heating unit. After passing under the softening unit, the film begins to harden as its temperature drops, thus causing the frost image to freeze whereupon the film passes under a second ultraviolet light exposure source which applies a uniform ultraviolet exposure over the whole of the film serving to harden and permanently fix the image. In simple inexpensive machines, this second ultraviolet light exposure may be accomplished by using the same light source from projector 13 used for the initial exposure of the film by passing the film on the opposite side of projector 13 from its initial exposure position and providing an opening in the back of projector 13. After uniform exposure, the film then passes onto a take-up roll 21 for further use as desired.

As should be apparent at this point, the two processes described above impose certain limitations upon the selection of materials which may be used in the process. Of course, the prime requisite of the materials utilized in the process is that they be able to form frost patterns. Reference is again made to the abovementioned copending application in the names of Gunther and Gundlach for an extensive treatment of selection techniques of frostable materials, their usable thicknesses, frost thresholds, as well as for a detailed description of the process steps and parameters of the frost process. Generally speaking, the most important property of frostable materials in most frost imaging techniques is that they be insulating at their melting or softening points so that deposited charge is maintained on them at least until the frost pattern is formed. It is generally also preferable, although not absolutely necessary, that material selected for the frost process be solid at ordinary room temperatures and that they be thermoplastic in nature.

In addition to being capable of forming frost images, the frost films utilized in the processes of this invention must have the additional capability of irreversibly hardening upon exposure to radiation such as ultraviolet light, visible light, beta rays or the like. This exposureinitiated hardening is to be distinguished from the reversible hardening, termed freezing, and softening of the frostable film with solvents or heat as they are applied upon initial formation of the frost pattern. In contrast, the exposure-initiated hardening acts to effectively diminish the solubility of the exposed layers and/or to increase their melting points. This change in the characteristics of the frost layers is believed to be caused by an actual change in the chemical structure of the materials in which their average molecular weights are increased, so as to raise their softening points and/ or increase their resistance to solvents.

One specific material which may be used as the frostable film according to the process described above is a partially hydrogenated rosin ester sold under the trade name Staybelite Ester-l0 by the Hercules Powder Company of Wilmington, Delaware. More specifically, this resin is made by the esterification of three acid molecules with glycerol. The major component, making up approximately 87% of the acid mixture is dihydroabietic acid. This acid may be said to be 50% hydrogenated derivative of abietic acid since two hydrogen atoms are added to it on average thus saturating one of the double bonds in the abietic acid. The remainder of the acid mixture comprises approximately 11% dehydroabietic acid and 2% abietic acid. For purposes of this explanation, dehydroabietic acid may be considered as fully saturated since all its double bonds go to make up one aromatic ring in the acid molecule which then will not readily add substituents while abietic acid may be considered as unsaturated since its two carbon double bonds may more readily add four hydrogen atoms in hydrogenation. It is thus seen that the major component of this resin is the glycerol ester of dihydroabietic acid which because of the three hydroxyl groups in glycerol will be referred to as a triester. The Staybelite Ester resin and an additional resin of closely related structure which is a viscous liquid at room temperatures and is sold under the trade name of Staybelite Ester-3 (a triethylene glycol ester of partially hydrogenated resin) have been found to form excellent frost images according to the technique of the above referenced copending application. It has also been found that these Staybelite resins in addition to having excellent frost properties may be hardened by exposure to ultraviolet light. Thus although the resins form good frost images and may be readily erased by resoftening for a sufficient period as described more fully above, they may be permanently fixed or hardened by ultraviolet light exposure, which both reduces the resin solubility in ordinary solvents for them (such as other esters, ketones, higher alcohols, glycol ethers, aliphatic and aromatic hydrocarbons, and chlorinated solvents) and significantly increases their melting point, with the degree of hardening depending upon the length of ultraviolet exposure. Althrough there is no intention to limit this invention to the following theory of operation, it is presently believed that the ultraviolet light exposure accelerates an aging process which occurs when the aforementioned Staybelite Esters are exposed to air for periods from about two weeks to a month or more. This is accomplished because the ultraviolet exposure eX- cites the remaining unhydrogenated double bonds in the abietic and dihydroabietic acid triesters so that ambient oxygen is added to form an epoxide at the double bonds followed by the addition of oxygen and/ or hydrogen from ambient moisture to form OOH or OH groups. This is believed to be followed by linking of rosin molecules through the oxygen of these groups so that a dimer, trimer or other short polyester is formed through the oxygen bridges. This theory has been verified to some extent by tests in which a number of samples of the Staybelite resin were formed in thin films and subjected to the same ultraviolet exposure source for varying lengths of time and then subjected to infrared analysis. As is indicated by the graph in FIG. 3 which compares the amount of ultraviolet exposure of the Staybelite samples with the size of the response at the hydroxyl band on infrared analysis, there is a very sharp increase in the number of hydroxyl groups formed in the early periods of ultraviolet exposure with the number of hydroxylgroups beginning to taper off asymptotically after about 1% to 2 hours of exposure. The increase in the hydroxyl band correlated well with increasing hardness in the films. This exposure was made with a high pressure quartz mercury vapor arc lamp manufactured by the Hannovia Lamp Division of Englehard Industries, Newark, New Jersey, Lamp Catalogue No. 30,620 containing a Watt 1.2 amp. lamp with the samples about 6" from the lamp. The lamp transmits the complete ultraviolet spectrum from about 1849 to 4,000 angstrom units.

Further vertification of the theory of hardening of the frost layers by oxidation or other reaction at reactive double bonds or other unsaturated sites in the resin molecules was given when an attempt was made to harden two saturated frostable materials (sucrose diacetate hexaisobutyrate and a low molecular weight polystyrene). These materials showed no permanent hardening after extensive intense ultraviolet light exposure and failed to show any increase in the hydroxyl band upon infrared analysis after the exposure.

Although the materials described above may be employed to carry out the described processes their speed of response to the hardening radiation is so slow as to make them impractical for many purposes. It has now been found, however, that when certain mixtures of materials are employed in the processes the speed of the system may be significantly increased Without detracting from their image forming capabilities.

The only requirements of these mixed systems are that the selected material combinations be frostable and hardenable by irradiation with actinic energy such as ultraviolet light, visible light, or the like. For example, one

other group of photohardenable polymers which may be used in these mixed systems include the cinnamate esters of polyvinylalcohol and/or of cellulose which may be further sensitized by the presence of anthrones and their derivatives, polynuclear quinone derivatives and certain ketones such as Michlers ketone. Hardening by photopolymerization may thus be accomplished either directly as by excitation of a pi electron in the monomer or by radiation activation of an included polymerization initiator. These materials are commercially available from the Eastman Kodak Company of Rochester, New York, under the trade name KPR or Kodak Photoresist. This type of polymerization system is more fully described in US. Patents 2,670,285, 2,670,286 and 2,670,287 and although these materials do not form good frost images with facility it has been found that mixed systems employing them are operable to great advantage in the process of this invention, where the two materials are compatible. Thus, for example, it was found that a oneto-two mixture by weight of the Staybelite Ester-1O described above with KPR was capable of frosting and had significantly faster irradiation hardening capabilities than Staybelite alone. It is believed that this was due principally to the much faster cross linking through the unsaturated side groups of the KPR rather than through the cross linking mechanism described in connection with the Staybelite resin, since hardening took place at speeds on the order of a few minutes, which is comparable to the hardening speed of KPR alone, rather than in the generally longer times (on the order of at-least one to two hours) which are required for hardening the unsensitized Staybelite. In this combination then, the high photosensitivity of the KPR is combined with the very good. frost image forming capability of the Staybelite. Thus in the mixture the good qualities of each component is found without the poor qualities of either. Resins which work well in the frost process but which are even incapable of hardenin upon irradiation with ultraviolet light or the like may also be mixed with other photosensitive polymers or polymer systems so that they may be used in the hardening mode of operation of the above described processes. Two examples of this type of combination comprise mixtures of Piccolastic A-50 with KPR and Piccolastic A-75 with KPR in equal parts by weight. The Piccolastics are low molecular weight polystyrenes available from the Pennsylvania Industrial Chemical Company of Clairton, Pennsylvania. These two mixed systems were tested and found to be capable of forming frost images and were permanently fixable with ultraviolet light exposures as short as 1-3 minutes. Further testing of films composed of only one of the constituents of the mixed films showed that the Piccolastics although capable of forming frost images could not be fixed by ultraviolet light exposure while with the KPR film it was virtually impossible to form a frost image but the film could be hardened by a short period of ultraviolet light exposure.

Another photosensitive mixed system employs nonphotosensitive polymers in the presence of photosensitive, low molecular weight compounds which react with themselves upon exposure to form a physical network throughout the exposed portions of the polymer, which network retards the rate at which solvents attack these portions relative to the unexposed portions. The system is operable with various frostable resins such as polystyrenes and coumarone-indene resins of the types described in the above referenced copending application and many other commercial plastics containing photosensitive chalcone or unsaturated ketone derivatives as more fully described in U.S. Patents 1,965,710 and 2,544,905. Exemplary frostable resins which may be employed in this type of system include Piccolastic A-50 and A-75 described above and Neville R13, a coumarone-indene resin marketed by the Neville Chemical Company. The proportions in the mixed systems have been found to be noncritical.

It should be noted that permanent hardening according to this invention need not necessarily increase both the softening or melting point and the insolubility of the frostable resin layer, since if one of the properties may be affected by exposure to actinic irradiation, the proper softening technique may be selected for use with this layer in the system.

The phrase permanent hardening as used in this specification and the appended claims is, therefore, intended to refer to a notable increase in the melting or heat softening points or increase in the degree of insolubility of a frost layer upon exposure to actinic irradiation. Permanent hardening need not take place through the whole thickness of the film but only to the depth to which the frost depressions form so that this hardening will truly fix the image.

The term polymerization as used in this specification and the appended claims is intended to be read in its broadest sense, regardless of the length of the polymer formed and to include cross linking of molecules, branching and the like as well as the formation of straight chain polymers of recurring molecular units.

By the term actinic as used in this specification and in the appended claims it is intended to mean electromagnetic radiation of sufificiently short wavelength to excite at least one ethylenic linkage or other reactive site in the molecular structure of film materials thus causing them to polymerize. For direct excitation of the linkage in most film materials this requires the use of electromagnetic radiation having a wavelength approximating that of the ultraviolet light range (below about 4000 A.). It is tobe noted, however, that indirect excitation with elecromagnetic radiation ranging into the wavelength of visible light may be employed when one of the sensi-tizers described above is present in the film although ultraviolet is generally the most efiicient in this regard. Thus actinic radiation is to be distinguished from the application of heat or heat producing radiation such as infrared since the energy applied in this manner tends to be shared by all of the vibrational modes of the material, rather than opening reactive sites within the material by selective excitation at these sites. Accordingly, by actinic radiation, in its broad sense, it is intended to refer to radiation having a wavelength equal to or less than that of visible light.

I claim:

1. A plastic deformation imaging film comprising a mixture including a substantial proportion of the esterification product of partially hydrogenated abietic acid and a photopolymer selected from the group consisting of cinnamic acid esters of polyvinyl alcohol and cellulose.

2. A plastic deformation imaging film according to claim 1 including a light sensitizing agent for said photopolymer.

3. The method of forming a plastic deformation image comprising the steps of:

(a) providing a film comprising a softenable material which has an electrical resistivity greater than about 10 ohm-centimeters at its softening point and is capable of accepting and mechanically responding to a charge pattern deposited on a film of said material to form surface wrinkles, and a photopolymer;

(b) forming an electrostatic latent image on the surface of said film;

(c) softening said film whereby the surface wrinkles in image configuration; and

(d) exposing said film to electromagnetic radiation of a frequency which causes polymerization of said photopolymer thereby permanently hardening and fixing said plastic deformation image.

4. The method of forming a plastic deformation image comprising the steps of:

(a) providing a film comprising a softenable material which has an electrical resistivity greater than about 10 ohm-centimeters at its softening point and is capable of accepting and mechanically responding to a charge pattern deposited on a film of said material to form surface wrinkles, and a photopolymer;

(b) exposing said film to an image with electromagnetic radiation of a frequency which causes polymerization of said photopolymer, until said film is significantly hardened in image areas;

(0) uniformly electrostatically charging said film,

and;

(d) softening said film whereby the surface wrinkles in those areas of the film which have not been hardened by exposure.

5. The method of forming a plastic deformation image comprising the steps of:

(a) providing a film comprising a softentable material which has an electrical resistivity greater than about 10 ohm-centimeters at its softening point and is capable of accepting and mechanically responding to a charge pattern deposited on a film of said material to form surface wrinkles, and a photopolymer;

(b) uniformly electrostatically changing said film;

(c) uniformly softening said film whereby the surface is uniformly wrinkled;

(d) exposing said film to an image with electromagnetic radiation of a frequency which causes polymerization of said photopolymer, until said film is significantly hardened in image areas, and;

(e) softening said film whereby the surface wrinkles are erased in thise areas which have not been hardened by exposure.

References Cited by the Examiner UNITED STATES PATENTS 3,202,508 8/1965 Heiart 96-115 FOREIGN PATENTS 1,254,024 1/ 1961 France.

I. TRAVIS BROWN, Acting Primary Examiner.

NORMAN G. TORCHIN, Examiner.

C. E. VAN HORN, Assistant Examiner. 

1. A PLASTIC DEFORMATION IMAGING FILM COMPRISING A MIXTURE INCLUDING A SUBSTANTIAL PROPORTION OF THE ESTERIFICATION PRODUCT OF PARTIALLY HYDROGENATED ABIETIC ACID AND A PHOTOPOLYMER SELECTED FROM THE GROUP CONSISTING OF CINNAMIC ACID ESTERS OF POLYVINYL ALCOHOL AND CELLULOSE.
 3. THE METHOD OF FORMING A PLASTIC DEFORMATION IMAGE COMPRISING THE STEPS OF: (A) PROVIDING A FILM COMPRISING A SOFTENABLE MATERIAL WHICH HAS AN ELECTRICAL RESISTIVITY GREATER THAN ABOUT 10**10 OHM-CENTIMETERS AT ITS SOFTENING POINT AND IS CAPABLE OF ACCEPTING AND MECHANICALLY RESPONDING TO A CHARGE PATTERN DEPOSITED ON A FILM OF SAID MATERIAL TO FORM SURFACE WRINKLES, AND A PHOTOPOLYMER; (B) FORMING AN ELECTROSTATIC LATENT IMAGE ON THE SURFACE OF SAID FILM; (C) SOFTENING SAID FILM WHEREBY THE SURFACE WRINKLES IN IMAGE CONFIGURATION; AND (D) EXPOSING SAID FILM TO ELECTROMAGNETIC RADIATION OF A FREQUENCY WHICH CAUSES POLYMERIZATION OF SAID PHOTOPOLYMER THEREBY PERMANENTLY HARDENING AND FIXING SAID PLASTIC DEFORMATION IMAGE. 